Check valves are commonly used in well hydraulic fracturing operations. Large pumps are connected by flow lines to a well for pumping a liquid such as water into the well at high pressures to fracture the earth formation. Various check valves are coupled into the flow lines to prevent back flow to the pumps.
A typical check valve has a body with upstream and downstream flow passages separated by a central cavity. A valve seat is pressed with an interference fit into the downstream flow passage. A flapper assembly is inserted through an access bore in the body for engaging the valve seat.
While this type of check valve works well, a high flow rate through the check valve may tend to cause the seat to dislodge from the flow passage. Other improvements are also desirable, such as simplifying the flapper assembly.